GeO 2 Encapsulated Ge Nanostructure with Enhanced Lithium‐Storage Properties

Germanium (Ge)‐based nanostructures, especially those with germanium dioxide (GeO 2 ), have drawn great interest for applications in lithium (Li)‐ion batteries due to their ultrahigh theoretical Li + storage capability (8.4 Li/Ge). However, GeO 2 in conventional Ge(s)/GeO 2 (c) (where (c) means the core and (s) means the shell) composite anodes with Ge shell outside GeO 2 undergoes an irreversible conversion reaction, which restricts the maximum capacity of such batteries to 1126 mAhg −1 (the equivalent of storing 4.4 Li + ). In this work, a porous GeO 2 (s)/Ge(c) nanostructure with GeO 2 shell outside Ge cores are successfully fabricated utilizing the Kirkendall effect and used as a lithium‐ion battery anode, giving a substantially improved capacity of 1333.5 mAhg −1 at a current density of 0.1 Ag −1 after 30 cycles and a stable long‐time cycle performance after 100 cycles at a current density of 0.5 A g −1 . The enhanced battery performance is attributed to the improved reversibility of GeO 2 lithiation/delithiation processes catalyzed by Ge in the properly structured porous GeO 2 (s)/Ge(c) nanostructure.